An Experimental Rig and Investigation of Steam Generator Tube Loading during Main Steam Line Break

Abstract

<p>Tubes in steam generators vibrate when subjected to cross-flow of secondary side coolant, particularly in the U-bend region. Such tube vibrations result in fretting wear at tube supports, reducing the margin of safety against failure. In the event of a main steam-line- break, the superheated water In the steam generator undergoes rapid depressurisation, resulting in a high-velocity two-phase steam-water flow across the steam generator tubes. This rapid blow-down phenomenon induces potentially catastrophic transient loading that is difficult to predict. Since the tubes represent the boundary between irradiated primary side fluids (deuterium) and the secondary side coolant, tubes in CANDU steam generators that cannot withstand the transient loading will leak irradiated primary side fluid into the secondary side, which passes outside of the containment building. The objective of this experimental study is to develop a better understanding of the transient loading and its prediction, such that structural tube failures can be avoided.</p>